1. Field of the Invention
The present invention relates to a gear coupling device and a gear coupling method which carry out operations for power transmission and power transmission switching by gears.
2. Description of the Related Art
Traditionally, a known gear device for an engine starting device includes gears having chamfered portions at its end surfaces for the engagement of the gears with each other for coupling the gears (refer to, for example, JP-2001-248710-A). The engine starting device couples the gears to each other only for starting the engine and thereby transmits power. When a start-up operation ends, the engine starting device uncouples the gears from each other. Since the gears remain coupled to each other only during the engine start-up operation, an unnecessary mechanical friction normally does not occur. Therefore system efficiency can be improved. Thus-configured system needs to conduct an operation for engaging the gears with each other, and therefore chamfering at the end surfaces of the gears is effective as described in JP-2001-248710-A.
In conjunction with coupling of rotary bodies, a control device provided with a phase control unit is known (refer to, for example, JP-2006-83919-A). The phase control unit controls a rotational state of a first engaging member based on a phase difference between a tooth of the first engaging member and a tooth of a second engaging member. The technique described in the JP-2006-83919-A is effective to switch gears of a geared transmission for a vehicle. In general, the vehicular geared transmission has a clutch mechanism and a decelerating mechanism using the gears. The clutch mechanism is a device for switching an operation for whether the gears are to transmit power or not. The clutch mechanism and the reduction mechanism are combined to thereby change a path for transmitting power and switch the gears, with the clutch mechanism achieving a smooth switching operation. When this system is used, however, the gears per se remain engaged with each other even if power is not being transmitted, which will generate an unnecessary mechanical friction.